BOX the frame??? Yah or Nay

hey there wheelers...

i am looking to pick up a new (to me) frame and put it under my 73 cj5. my current frame twists, flexes, and tweaks to the point that it keeps ripping my body (the jeep) and stressing the mounts.

when i get this frame i intend to recondition the thing to better than new; sand, repair if needed, weld, better crossmembers/transfer case mounts, repaint, and planning on boxing it. however, i have read numerous articles giving reasons not to box the frame, as it will cause the frame to crack where it should be flexing and it causes more stress to the frame and will in turn give me more problems down the road. i know this frame is considered the 'rubber frame' and that is where i get the extra articlulation and suspension travel, i just feel like it is stressing my jeeps body too much. (example-if the front right is at full tuck, and front left is at full drop, my clutch pedal hits the floor, when pressed, and barely disengages the clutch. this is from my body trying to peel away from the frame as it is twisting with the suspension). this, to me, is BAD!

i am from the school of thought (maybe this is because i am under 30?!) that a frame is meant to be strong, rigid, and not flexible (or very little if at all), they should be boxed (much like frames of today are made), and strong as hell to keep thier shape and let the suspension do all of the work. i hate the feeling of articulating to the point of my jeep curling up like a canoe!

for those of you wondering, this jeep's purpose is trail use only, the only street she sees is driving around the block to keep parts moving and to be sure she is running well. i want to think long term when setting this frame up. my future aspirations for this jeep are dana 60's, slightly longer wheelbase (?), linked suspension front/rear (?), 35"+ tires (without being too large). so, i would like for this frame to be AS STRONG AS POSSIBLE to accept whatever crazy suspension i attach to it in the future.

one example i like and was aiming to follow is the big lime ( http://www.earlycj5.com/featured/reighard/ )...i like the frame build, as well as the way the reinforcements go upward, where i plan on tying the roll cage to the frame. i do not know who's this is however to see if he had any issues as far as boxing the frame.

so, the big question: BOX IT OR NOT???

other questions include:
:? what type of paint or coating is best for the frame?
:? shackle reversal for the front? (it is trail use only)
:? best lift options- SOA vs. 2.5" lift vs. 4" lift...i just purchased 33's that rub like hell. i though fender trimming would do it for me-WRONG! i was thinking a 2.5" leaf sping lift might do it, but everyone on here posts getting a 4-4.5" leaf spring lift to clear 33's.
:? any other opinions, recommendations, or experiences are greatly appreciated.

thanks all, happy wheelin'

 

The only cracks I personally have had when boxing a frame is any part that I left unboxed. Like right at the end of a spot you might leave open...it cracked. After boxing the entire frame end to end...I have not had any breaks.
Rigid frame vs flexible is one of those "iffy" kind of questions. For a hundred years...I was always told that you want the frame to flex...it will ride better, etc, etc. But...these days I hear the opposite "let the suspension do the work not the frame"...I think there can be valid points made for both...I personally went with the strong frame approach...but I think it was more out of habit than it was out of research...Because I have built A LOT of long travel sand rail frames...a couple of desert racers...and I always went with a strong frame and good suspension (and I have always been happy with the way they turn out)...So I just stayed with the same theory when boxing my Jeep frame...Even though the two things are really apples and oranges. Either way...works good for me.

 

you could strap it instead of boxing
same result, easier to install

 

No stress risers with strapping too.

 

I was always told that for straight line driving and or racing applications a boxed frame is the ticket and for wheelin you want the flex of the frame a little. This is what I have been told by the old timers. With today's suspension technologies though I would personally prefer to have a strong/stiff frame and let the suspension do the work. I have also experienced alot of body movement when I had my K5 Blazer. Once I put in a full roll cage (welded to frame) I completely eliminated body movement but by the same token I started ripping out body mounts and lost some articulation as well. How does "strapping" work?

 

I'm not too familiar with the strapping thing, but I do agree with the fact that some vehicles need a boxed frame and some don't. Vehicles like a pickup truck, especially a long wheelbase one, and most vehicles with leaf spring suspensions, need to have some flex in the frame. However, when I look at a Jeep, since the tub is all one piece from the back all the way to the firewall, I don't want the frame to flex. To me, any shorter vehicle like that is better off with a boxed frame unless you're using it mostly as a daily driver on the road. As for the lift, I would try to go with a suspension lift instead of the spring over, and if you've already done the fender trimming, anywhere from 2.5 to 4 should be fine. I like the 2.5" on the CJ5's to keep the center of gravity low, especially if you've already done some fender trimming on it anyway.

Just my .02

 

i'm putting a bds 2.5 inch lift spring kit on my 73 cj5 to get more room for the tires. i also put 2 inch wide wheel spacer on just for the heck of it. my jeep came from the dealership new with the 8000lb ramsey pto winch on it and i noticed that from the front frame horns back the frame is boxed about two feet. if you want to go soa rocky-road outfitters makes a very easy bolt on kit that is tough and well built. but i would not combine the 2.5 lift springs with the kit use stock leaf springs b/c that will stretch evrything out.

 

ok, thank you so much for the input, now i have a few new questions...

:? will somebody please explain strapping to me...
-i'm guessing it is attaching a strip of steel to the outside (or inside i guess) of the wide part of the frame, instead of boxing it? just a guess...

warloch
-as for the saginaw conversion, i already have have power steering up there, i've had issues in the front but that was just the p/s box, p/s box mount (near impossible to find a replacement), steering rod stripping,coupler falling apart, and the upper coupler/u-joint stripping...JUST got that all replaced and back together, i could NOT believe all that broke at the same time.
sorry, off on a tangent, so you say only box near the p/s box? why is this, and would you not get cracking at the end of the boxing? please explain a little bit more.

i am definately going to throw some wheel spacers on, probably the 2" myself. i see sets of 4 on ebay for just over $100 rather than spending the $100/pair elsewhere. those wide tires i got rub on the shock mounts in the front end when turned and tucked.

my lifting options...
my current springs (probably stock) are saggy, wait, i mean SAG-GY. either way i should and need to replace the springs. i will either do replacement stock springs and go SOA, stock yj springs and SOA, or a 2.5", or a 4". (if i purchase lifting springs, i will leave them UNDER the axle). i have planned, untill recently, of doing a SOA and replacing the springs, preferring to go with yj springs. i am under the impression that stock springs above the axles will give me that lift i need (+/- 5"), and actually provide more leverage on the axle for increased articulation. my largest concern is rear driveshaft angle...

i mentioned that i was interested in the 2.5" lift. after seeing how much my tires rubbed front and back, i questioned it, then it seems everyone posting here, is getting 4" for their rigs. i think that may be because they don't trim fenders? i did trim my fenders already, well just the front, nto rear yet. does anyone know a 2.5 will fit or do i NEED the 4"? once again, these tires are 33x14.00x15r, wheels are 10" wide, with a large offset, but still need spacers to clear the front shock mounts, and stop rubbing the frame.

why does nobody like the SOA lift?

below are a couple pics of my rig showing the fender trimming and some tire rub in the front and rear, if i posted them right.
thanks for the help guys

also, does anyone know the jeep on here that i was referring to -the big lime?

 

Yea I know big lime. But it looks nothing like that anymore. now it's a tube buggy. Eddie is a hell of a fabracator. I sent you a PM.

 

The C-channel has a top, side, and bottom - the top and bottom are the rails and the side is the web. Strapping puts a strap (say, 3/16" thick - roughly the same thickness as the channel stock, and narrower than the rails) along the length of the rails. These are typically stitch welded along their length, say 1" of weld and 2" with no weld. I have seen this method used to good effect on Baja race cars with Jeep C-channel frames.

The strap ideally would extend the full length of the frame. The CJ-6 uses a strap along the bottom of the frame, between the front and rear spring hangers, to good effect.

Note you don't want to weld across the frame - keep your welds parallel to the tension/compression of the strap. Welding perpendicular to the long axis of the frame will create a stress riser that could be the origin of cracks.

I expect the strapping won't make the frame super stiff, and I think this is what you want. If you box, you'll definitely make the frame much more rigid. Depends on whether you are interested in strength or rigidity. Remember, steel will strain (bend) forever as long as the strain limit is not exceeded - no metal fatigue. This is different from other metals such as aluminum or copper, where even the effects of small strains are cumulative (this is why airplane fuselages must be retired after a certain number of hours in the air).

Ideally you'd like to distribute the stress evenly along the length of the frame. If you have a stiff section next to a rigid section, walla - a stress riser (where the stress rises) at the junction. This is what happened when Chuck boxed part of the frame. This is what happens to the intermediate frame at the front cross-member - stiff cross-member next to a flexible frame, and it cracks at the corners. Same thing happens at the spring hangers... that short, rigid section is enough to concentrate the forces.

 

My opinion is that non-boxed frames are probably as much a product of the bean counters as much as any concern for ride or durability. A street or mild trail vahicle probably benefits a lot from a flexy frame as it adds some functionality to the suspension.

However, once you start using the vehicle in ways that weren't intended, you need to beef up the entire vehicle for it's new use. To me, for heavy trail use, that means boxing the frame (or building a new one from box tubing), and building a suspension that works in the new environment. Sure, our frames flex, and will probably last a good long time on rocky trails, but they will fail a lot faster than if the vehicle never sees anything worse than a dirt road. For durablility, box the frame, then add at least an 8-point roll cage tied into the frame to make it as rigid as possible. Then the frame will be equipped to deal with the added stress of a lot of suspension flex, and the body will become what it's supposed to be any way, a tub to protect the occupants from the elements, instead of a stressed member of the suspension.

 

strapping top and bottom will strenthen the frame a BUNCH; be prepared to re-learn how to drive off road if you full length box as well.
the frame will be so rigid that any axle tweaker will get you way up in the air with little notice; the flex will be gone; the photo op people will love you to death with the wheels that high in the air; and you'll have to be careful as to not go over.
ymmv

 

I strapped the bottom only on my frame and had a crack form and go right through the strapping. Now I'm working on a full box frame. That being said, I have a 4" Soft Ride spring set and it flexes like crazy. I don't need to have the frame and body being used as part of the suspension system. As was stated earlier in this post, we use these Jeeps for trails that they were never really designed for. Early Broncos had fully boxed frames and I've never heard any complaints about their off-road ability. Personally, I think this "frame-flex" concept is not much more than an excuse for the "under-engineered" frames put out by Jeep. Yes, Jeeps are very capable for light to moderate trails right out of the box. But if you have the chance to consistently run difficult or extreme trails you can discard most of the stock Jeep engineered parts. Or spend a lot of time on the trail being a mechanic. Just my .02, but with some experience.

 

I could not agree more. Many of us are pushing these vehicles SO far past what they were intended to do. We build every part of them to tackle the type of terrain that previously was only possible by construction and logging equipment...We go with bigger tires, lift to clear the big rubber, flexy springs, stronger axles, stronger transmission, transfer cases...well, the list goes on and on. These modifications will take your Jeep and it's stock frame into spots never dreamed of by the folks who designed that frame years ago. I feel that if your going to do modifications to your Jeep to make it capable of traversing some of this extreme terrain...then you probably should not stop at the frame.

You will have to take everything I say here with a grain of salt for several reasons...because I have no concrete evidence that boxing a Jeep frame is better than an unboxed frame...what I am saying is nothing other than opinion...and my opinion of boxed being better is based on an entirely different vehicle than a Jeep.

Speaking of that entirely different vehicle...When a myself or other fabricators build a tube frame for a sandrail...we try to design it to have as little of frame flex as possible. We are realistic and we know that a rail hitting a large jump at 80MPH and sailing close to 200 feet IS going to have some frame flex. But we try to keep that flex to an absolute bare minimum...because the flexing will cause cracks soon. When we find an area that has cracked...the next frame built will normally have that area addressed with a different design that hopefully will lead to less flex.
I personally have had two stock CJ frame break on me...and not under conditions that I would have even considered out of the ordinary. So I guess my thinking this time around was..."let everything else break and make the frame strong." Only time will tell if that was a good idea or not..I'm a little over seven years with no problems, But my Jeep does not see the same kind of abuse that I see some of you guys putting yours through...So maybe I'm all wet.

 

As an afterthought on strapping, you'd really need to remove the spring hangers and run the strapping all the way from end to end, then re-install the hangers. Otherwise you risk having the frame crack right at the spring hangers where your strapping would stop. That's where the frames like to crack anyway.

 

As for full boxing of the frame. The assumption seems to be that you lose all the flex. Let's face it, it's steel. If you apply force to it, it is still going to flex. just not as much. Flex any piece of metal enough times and it will break. The frame I'm working on will be fully boxed, but I'm going to make liberal use of the holesaw on my boxing, both for drainage and to allow for some movement.

 

I think a lot of people don't like the SOA because they have seen many of them engineered poorly. Mostly on street driven Jeeps. Steering geometry gets out of wack and it becomes dangerous. I have heard though, that spring over with wrangler springs flexes like mad, but have no experiences with it. If I ever do a spring over which isn't likely, I would lengthen the wheel base as well and probably go full width. Being that tall and top heavy it wouldn't take much to roll over.

I think I have been on pirate4X4 too much latelyR)

High5

 

Too bad there's no scientific way to test all the possible variations. None of us have enough time or resources to be certain that any of these frame mods are optimal. I like the strapping approach because that's what I saw done to the race cars back in the 70s, and because it appeals to my physical intuition. Others like the boxing approach, because they've tried it, and it seems to work out ok.

Given all this anecdotal and unrepeatable evidence, I'd think you'd want to go at making changes with some caution. If it were me, I'd try and figure out the easiest approach that requires the fewest changes and the least amount of steel. From my POV, the exact wrong thing to do would be to throw 300 lbs of steel at the frame ... I wouldn't want to have to drag all that weight around if it didn't serve some good purpose, and the law of unintended consequences will apply. The more you change, the more likely there will be some (unintended consequences). If you can figure out an incremental approach to adding steel that seems right to you, I'd say go to it, and report back along the way.